If you’ve used Photoshop’s rulers at all, you know that you have your choice of either a vertical or horizontal guide. That’s not a bad thing, but there’s one thing missing—a diagonal guide. Since Photoshop doesn’t have one, here’s a tip for making your own: Start by clicking the Create a New Layer icon in the Layers palette, then double-click on your Foreground color swatch and in the resulting Color Picker, set it to R: 161, G: 253, B: 253 (the color Photoshop uses for its built-in guides). Switch to the Line tool found in the Shapes tools (Shift-U until it comes up), and on this new layer draw a diagonal line where you want your guide to appear (make sure you have Fill Pixels icon selected in the Options Bar). It’s not a bad idea to copy that layer into a separate document and save it on your drive—so anytime you need a diagonal line, you can just open that document and drag it right in.